1. Field of the Invention
The present invention relates to apparatus for lowering and retracting landing gear for aircraft. A single motor operates plural drives each retracting and lowering one or more wheels, so that all wheels are lowered and retracted simultaneously.
2. Description of the Prior Art
Landing gear for current aircraft designs provides for taking off and landing with the landing gear in the deployed position and for flight with the landing gear retracted, except for a limited number of small aircraft having landing gear fixed in the deployed position. The landing gear generally includes a vertical support strut and an inclined stabilizing strut for each wheel assembly, wherein the vertical and inclined orientations are defined when the landing gear is in the deployed condition. Both struts are pivotally mounted to the aircraft.
Some prior art arrangements allow for simultaneous lowering and retraction of landing gear. Examples are seen in U.S. Pat. No. 1,958,486, issued to Nicholas J. Medvedeff on May 15, 1934, U.S. Pat. No. 2,262,330, issued to Charles I. MacNeil et al. on Nov. 11, 1941, and U.S. Pat. No. 2,446,415, issued to Cedric H. Flurscheim et al. on Aug. 3, 1948, and U.K. Patent Number 527,281, dated Oct. 4, 1940. MacNeil et al. employs a screw shaft drive which acts on an inclined strut to urge a wheel into deployed and retracted positions. However, MacNeil et al. lacks a universal joint arranged to maintain a section of the screw shaft parallel to the inclined strut, as seen in the present invention. MacNeil et al. must anchor both ends of the screw shaft in addition to providing a threaded collar which travels along the screw shaft. In the present invention, the threaded collar assists in securing or anchoring the screw shaft. Operation of MacNeil et al. is opposite that of the present invention. MacNeil et al. pushes the wheel away when retracting, whereas the present invention pulls the wheel into the retracted position.
Medvedeff also employs a screw shaft drive, but supports the weight of the aircraft on the screw shaft. This is avoided in the present invention. Instead, the inclined strut in the present invention is acted on by the screw shaft drive.
The device of Flurscheim et al. retracts the wheel in arcuate motion sweeping through fore and aft along the fuselage in a vertical plane. By contrast, the wheel in the present invention sweeps through a torroidal path having an axis parallel with the longitudinal axis of the aircraft.
In the U.K. patent, wheels are moved by gears. By contrast, the present invention employs a screw shaft drive. There is no possibility of providing a screw shaft which remains parallel to an inclined strut acting on the principal, weight bearing strut supporting the wheel.
In U.S. Pat. No. 2,446,528, issued to Edgar A. Clark on Aug. 10, 1948, a screw shaft drive retracts the wheels. However, the screw shaft is fixed relative to the fuselage, whereas in the present invention, a universal joint arrangement enables the screw shaft to remain parallel to an inclined stabilizing strut as the strut changes its orientation relative to a horizontal direction.
A wheel deployment and retraction scheme seen in U.S. Pat. No. 2,740,135, issued to Charles P. Church on Apr. 3, 1956, features a toothed rack drive. However, when retracting, the wheel moves in a vertical plane in a manner similar to Flurscheim et al. In the present invention, the wheel sweeps through a toroidal path having an axis parallel to the longitudinal axis of the aircraft.
A retraction scheme shown in U.S. Pat. No. 2,185,235, issued to Oscar A. Swanson on Jan. 2, 1940, causes the weight of the aircraft to be imposed on the screw shaft in a manner similar to Medvedeff. This is avoided in the present invention.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.